Cold beverages are especially popular during the warmer months of spring, summer, and early fall. Yet, when one participates in outdoor activities, his drink will warm under the blare of the hot sun. The drink within the beverage can warms because heat and electromagnetic radiation from the surrounding environment will transfer across the surface of the can and into the drink. Indeed, heat transfer is driven solely by the difference between the temperature of the environment and the temperature of the soft drink.
Heat transfer occurs through three mechanisms: conduction, convection, and radiation. Conduction refers to heat transfer that occurs across a medium such as a warm hand touching an aluminum can. Convection refers to heat transfer that will occur between a surface and a moving fluid when they are at different temperature. In this instance, the moving fluid could be a warm summer breeze. Thermal radiation occurs because all surfaces of finite temperature emit energy in the form of electromagnetic waves. The sun emits electromagnetic waves which travel through space and retransform into heat when they strike an absorbing object. The waves can also be substantially reflected away by a reflective object. Hence, even in the absence of an intervening medium, there can be net heat transfer by radiation between two surfaces at different temperatures.
A beverage cozy, also known as a "coozy," is a cylindrical device designed to snugly fit around a standard aluminum beverage can. In general, these devices are made of an insulating material. The device inhibits heat transfer by preventing convective heat transfer from a large percentage of the can's surface area. The cozy also inhibits conductive heat transfer by presenting a material with a low heat transfer coefficient adjacent to the highly conductive aluminum can.
Various patents have issued involving beverage insulators. For example, U.S. Pat. No. 4,872,577 to Smith discloses a hinged closure attachment for insulated beverage can container. The closure attachment comprises an annular band, a lid of insulating material to match that of the container, and hinge means mounting the lid on the band. The lid is in the form of a low-profile inverted cup and is diametrically dimensioned to overlie the top of the marginal edge of the container. The band tightly encircles the marginal edge of the container. The hinge contains a spring biasing the lid to the closed position.
U.S. Pat. No. 4,720,023 to Jeff discloses a combination insulated mug and beverage can holder. The holder is comprised of a one-piece flexible ring-shaped retainer with an annular groove that mounts on the upper rim of an insulated mug. When the retainer is fitted to the mug's upper rim, the insulated mug functions as an insulated holder for a beverage can. When the retainer is not attached, the mug functions as a normal drinking vessel.
U.S. Pat. No. 4,540,611 to Henderson discloses a one-piece insulator for beverages. The device is cut from a sheet of insulative foam and laminated with a surface vinyl film. The holder pattern is folded over on itself and the side edges are stitched or vinyl welded together.
U.S. Pat. No. 4,372,453 to Branscom discloses an insulated container holder as well. The cylindrical holder is made of either a rigid foam or may be of double wall construction to provide thermal insulation. A pivotal cap is received by the cylindrical holder, said cap having a central opening overlying that of the cylinder. After a beverage can is inserted, this cap is pivoted, thereby gripping the can.
U.S. Pat. No. 4,293,015 to McGough discloses an insulated beverage cozy comprised of a cylindrical body with an inner wall and an outer wall. These walls are fastened together to form a plurality of compartments for holding goose down or other insulative materials. An elastic top band is attached to the top of the cozy to hold it snugly to the beverage container.
Each of these designs is useful at blocking against conductive and convective heat loss from the sides and bottom of the can. However, the devices illustrated in the patents to Jeff, Henderson, Branscom and McGough fail to inhibit heat transfer across the top of the beverage can. While the device illustrated in the patent to Smith covers the top of a can with insulation, the device is cumbersome and must be held back when the beverage is consumed. Therefore, a need exists for a beverage insulator which inhibits the warming of cold drinks in beverage cans placed into the insulator by reducing conductive, convective, and radiative heat transfer across the surface of the can. The device must allow easy insertion of the can therein. This device should have easily adjustable means to shade the top of the can from the sun's rays, thus inhibiting the warming of the can's top and the drink contained therein. Also, this means to shade should be easily retractable to allow access to the top of the can.